Most "metal polishes" contain Aluminum Oxide as it's abrasive. Flitz, Blue Magic, Simichrome, and a hundred others all contain.. Aluminum Oxide as the polishing agent. (A GOOGLE of the ingredients of the product will reveal what it contains ) They all will advertize it as " Non-abrasive" because the oxide is fine enough to be below Federal guidelines. But it IS simply an Abrasive.... So in effect one is Grinding down any scratches in the surface of the object. Elbow grease and a little patience and you MAY be able to brighten up the surface. It's called Buffing. It's the same thing that is done to polish and shine the plastic at the time of it's manufacture. Plastics Dealers like TAP Plastics can advise as to which product is best.
In a good many polish products Kerosene and Mineral spirits are used to hold the abrasive . Some polishes have ingredients that leave a "protective" surface. These ingredients MAY or may not have negative results on some surfaces. Use caution. Advertisements and Anecdotal experiences.. notwithstanding... One should always check the product's ingredients.. Before using. Uniform Whisky, Ralph Ahseln "Oblio" Lying: Portland OR
